1. Field of the Invention
This invention relates to a photoluminescent compound, more particularly to a photoluminescent compound which emits light via an intramolecular interaction of an imino group and an electron-donatable moiety. This invention also relates to a photoluminescent organic composition which emits light via an intermolecular interaction of an imino group and an electron-donatable moiety.
2. Description of the Related Art
Fluorescence technique is being applied increasingly. With the assistance of fluorophores, many biological processes can be visualized at the molecular level. In recent years, there has been a dramatic proliferation of research concerned with the development of effective fluorescent materials. A wide variety of fluorescent species, such as organic dyes, metal-ligand complexes, quantum dots, and metal nanoclusters, have been synthesized, for a variety of applications.
Organic dyes are the molecules most commonly used as reporters in fluorescence sensing, due to their availability, low price, and versatility. However, the rapid photobleaching of the organic dyes limits the degree to which they can be practically applied. Additionally, the organic dyes usually contain lipophilic aryl rings, which have potential toxicity and which can not be easily applied in the biomedical field in which high hydrophilicity is desirable. Therefore, further processing is required to improve the hydrophilic property of the organic dyes.
Quantum dots and metal nanoclusters show greatly improved photostability, and are emerging as fluorescent reporters with properties and applications unavailable to traditional organic dyes. The performance of the quantum dots and the metal nanoclusters arise mainly from their unique size-dependent optical and electrical properties as the material-unit drops below a certain size. This size is typically between several to tens of nanometers for most of the quantum dots and only several to tens of atoms for the metal nanoclusters. In addition to optical properties and ultra small size, noble metal nanoclusters are highly attractive for biolabeling and bioimaging, due to their nontoxicity compared with the quantum dots.
Nonetheless, the severity of the size requirements pertaining to metal nanoclusters makes the preparation and long-term stability of these species a challenge that has greatly hampered studies of their fundamental properties, and investigations to broaden the range of available applications.